On Thu, 20 Feb 2025 20:57:47 GMT, Archie Cobbs <aco...@openjdk.org> wrote:
> This PR is a prototype to stimulate discussion of > [JDK-8261669](https://bugs.openjdk.org/browse/JDK-8261669), which seeks to > add more warnings when an implicit cast of a primitive value might lose > information. This can possibly happen when converting an `int` to `float`, or > when converting a `long` to `float` or `double`. Java does not require an > explicit cast for such assignments, even though they may result in > information loss. > > I'm interested in feedback both on whether this is a good idea and also the > approach taken - thanks! > > Currently, we generate this warning, but only for assignment operators, e.g.: > > int x = 0; > x += 1.0f; // warning here > > > This PR would add warnings for two additional cases, (a) regular assignments > and (b) method parameters, e.g.: > > void method(float f) { } > ... > float a = 0x10000001; // warning here > method(0x10000001); // warning here > > > It would _not_ generate a warning in cases (a) and (b) when the value is a > constant value and we can determine that no information would be lost, e.g.: > > float f1 = 0x10000000; // no warning here > > The definition of "no information would be lost" is that a round trip results > in the same value, e.g., `(int)(float)x == x`. In the examples above, > `0x10000000` survives the round trip but `0x10000001` does not. > > As usual, warnings can be suppressed via `@SuppressWarnings` or by adding an > explicit cast: > > > float a = (float)0x10000001; // no warning here This pull request has been closed without being integrated. ------------- PR: https://git.openjdk.org/jdk/pull/23718
